Studies designed to elucidate biological factors in anxiety disorders are proposed, with specific emphasis on the psychobiology of the panic attack. Twelve broad areas of study are planned: investigation of ventilatory physiology, development of a simple method for carbon dioxide induction of panic, study of the putative role of serotonergic transmission in anxiety, comparison of various laboratory methods of panic induction, further attempts to understand the mechanism behind lactate induction of panic, study of cognitive factors in anxiety and the role of breathing retraining in the treatment of panic attacks, development of a respiratory ambulatory monitor to study anxiety in vivo, location of objective biologic markers of panic during laboratory and ambulatory monitoring, continuation of work on the relationship of mitral valve prolapse to panic, collaboration in family studies of anxiety disorder using biologic probes, beginning of work to use genetic recombinant techniques to locate the putative disease gene for panic disorder, collaboration in on-going studies of social phobia and obsessive-compulsive disorder. Professional growth in the areas of brain imaging, molecular genetics, and serotonergic receptor physiology is also detailed. The goal of this work is to define the biologic basis for anxiety disorder, including validating a newly developed hypothetical neuroanatomical model for panic attacks, which will also integrate data from cognitive and learning theory experiments.